(1) Field of the Invention
The present invention relates to benzylated lignocellulosic substances and a method for producing same, and more particularly to benzylated lignocellulosic substances suitable for use as material to be foamed for the production of foamed molded articles without the addition of a plasticizer and a method for producing such formed articles.
(2) Description of the Prior Art
The recent growth of the petrochemical industry has brought about the production of various kinds of plastics. However, since plastics produced in the petrochemical industry are not biodegraded by microorganisms in nature, vast amounts of accumulated plastic waste cause a serious waste disposal problem.
One of the attempts which have been made to solve this problem provides for the collection of used plastic products and the decomposition decomposed of same in chemical reactor so as to produce recycled products. However, the practical use of such recycling is considered difficult for the following reasons. First, the cost of the collection is higher than the manufacturing cost of plastic products. Another reason is that, since a high temperature and a corrosive environment are generated in burning the plastics, the reactor is subject to severe damage, causing a high maintenance cost for the equipment. Order these circumstances, there has been a pressing need for the development of substances which can replace plastics manufactured in the petrochemical industry. Such substances should be easily moldable and should possess sufficient physical properties (e.g., strength) to withstand practical use, as well as biodegradability.
Wood is a typical, natural, high molecular weight lignocellulosic substance, which contains cellulose, hemicellulose and lignin as main components. Such lignocellulosic substances do not have thermoplasticity in themselves so that it was thought to be virtually impossible to mold high molecular weight lignocellulosic substances into various shapes in the same manner as plastics manufactured in the petrochemical industry.
Nobuo Shiraishi, one of the inventors of the present invention, has found that thermal flowability can be imparted to etherificated or esterificated wood flour by hot pressing and he has introduced, in the past, etherificated wood flour and esterificated wood flour as lignocellulosic substances having plasticity. In general, lignocellulosic substances having plasticity are more brittle than plastics manufactured in the petrochemical industry and inferior to the latter in physical properties such as strength. Of the lignocellulosic substances having plasticity, etherificated lignocellulosic substances have comparatively high softening points and suitable physical properties. Of etherificated lignocellulosic substances, particularly benzylated lignocellulosic substances exhibit high softening points and suitable physical properties. Further, the voluminous spatial configuration of benzyl groups in benzylated lignocellulosic substances provides steric hindrance, reducing the degree of the substitution of hydroxyl groups in, for example, a glucose residue contained in wood. In turn, by virtue of the reduction, which of the degree of substitution, hydroxyl groups remain in the substances, thereby permitting biodegradation to take place in nature.